Catalytic reforming process



cgs, KUHN, JR CATALYTIC REFORMING PROCESS July 16, 1946.

2 sneaks-sheet 1 Filed Aug. 22, 194g INI/- N TOR By WJ ATTORNEY PatentedJuly 16, 1946 C ATALYTIC REFORMNG PROCESS Carl S. Kuhn, Jr., Dallas,Tex., assgnor to Socony- Vacuum Oil Company, Incorporated, New York, N.Y., a corporation of New York Application August 22, 1942, Serial No.455,775

`carburetionand uneven burning, This is recognized by users, and thisrecognition is reflected in purchasing specifications which requirereasonable distribution of material across the entire boiling range ofthe fuel. Such requirement is usually arrived at by specifying that theproduct 2 Claims. (Cl. 260--683.4)

`arrangement to yield a mixture of branchedbe such that only givenpercents of it shall disf till over at each of several given`temperatures in the boiling range.

During recent years production of high octane value gasolines bysynthesis from lighter hydrocarbons has assumed increasing importancean-d widespread usage. Thus, for example, in processes known to the art,high octane gasolines may be prepared by alkylating normally gaseousisoparaiiins with normally gaseous olens in the presence of suchcatalysts as sulfuric acid, phosphoric acid, aluminum chloride, etc.Likewise, in my copending application S. N, 320,097, led February 2l,1940, there is disclosed a similar alkylating process using hydrogenfluoride as a catalyst. Branched-chain hydrocarbons of high octane valueare prepared also by polymerization of gaseous olens, and the polymersare usually hydro- -genated to give a saturated product.

Since alkylation processes, as usually conducted, eiect predominantlythe condensation of one particular isoparafn with one particular olefin,the resulting alkylate gasoline, although of high octane value, iscomposed essentially of branched-chain isomers of one parafflnichydrocarbon. Therefore, the alkylate is of relatively narrow-boilingrange, or, at least, it does not have a. required uniform distributionof hydrocarbons across the desired gasoline-boiling range. This is oneof the reasons why alkylate gasoline is now conventionally blended withgasoline of inferior anti-knock value in order to form blended gasolineof proper distillation characteristics and vapor pressure.

Accordingly, it is an object of this invention to provide a process fortreating a relatively narrowboiling fraction of branched-chainhydrocarbons so as to promote a molecular conversion or rearchainhydrocarbons which boils over a relatively wide range, Another object isto afford a process for treating a relatively narrow-boiling fraction ofalkylate gasoline or similar gasoline, consisting essentially ofbranched-chain hydrocarbons in order to yield a complete aviationgasoline of not substantially less octane value. Still another object isto provide a process for synthesizing a complete aviation gasoline fromgaseous hydrocarbons. These and other objects will be apparent from thefollowing description of my invention.

My invention is based upon the discovery that if a relativelynarrow-boiling fraction of gasolineboiling, branched-chain hydrocarbonsis treated in the presence of an alkylation catalyst under alkylatingconditions of temperature and pressure for a, controlled period of time,a gasoline fraction having desired distillation characteristics may beproduced therefrom. If desired, the narrow-boiling fraction may bereformed to produce a complete aviation gasoline having the properdistillation characteristics. Moreover, the gasoline-boiling productformed by my process possesses substantially as high an octane rating asthat of the original narrow-boiling, branchedchain hydrocarbon fraction.

In general, the conditions under which the alkylation catalysts reformalkylate or other narrow-boiling hydrocarbons are essentially the sameas those under which they will produce alkylate from lighter paraiiinsand olefins, except that sufcient additional reaction time must beprovided to obtain a reformed product of the desired characteristics,Thus, for example, when a catalyst consisting essentially of hydrogenfluoride is used, the hydrogen fluoride should be of at least aboutconcentration, and a temperature preferably between about -lO and about+30 C. should be employed. It is to be understood, however, that sincehydrofluoric acid, unlike sulfurie acid, is not an oxidizing acid,rather high temperatures up to about 200 C. may be used if desired.Since it is generally preferable to operate with the hydrocarbons in theliquid phase, the critical temperature of the hydrocarbon being reformedwill frequently set the upper temperature limit for liquid phaseoperation. The alkylating conditions for such catalysts as sulfuricacid, aluminum chloride, etc., are well known.

As stated previously, the reforming reaction is preferably carried outwith the reactants in the liquid phase and therefore sufficient pressureis eficaces used to maintain the reactants in this liquid phase.Suitable agitating means should be provided in order to afford efficientcontacting of the hydrocarbons and the catalyst as is customary in thealkylation art. Liquid phase operation is not essential, however, andlower pressures may be used if desired.

The relative proportions of the catalyst to the total hydrocarbons aresimilar to those used in alkylation processes. Within certain limits,increasing the amount of catalyst increases the amount of reformingobtained in a given time. In the case of solid or immiscible liquidcatalysts, and to a certain extent with a soluble catalyst, increasedagitation increases the amount of reforming obtained in a denite timeperiod since the agitation produces better contact between the catalystand hydrocarbons.

Alkylation reactions are generally carried out in the presence of alarge excess of isoparans. In this respect, as well as in the reactiontime, the reforming reaction is different. The amount of excessisoparaiiin over that required to combine with the olen is generally ofthe order of upwards of 460 mol percent in the case of alkylationreactions. In contrast thereto, reforming reactions will proceed mostrapidly in the absence of additional isoparaihnic hydrocarbons, althoughlimited amounts of light isoparafiins or high-boiling, saturatedhydrocarbons up to not over` 100 to 200 mol percent of the hydrocarbonbeing reformed, may be present as will be discussed more in detail laterin the description of my invention.

rIhe exact reaction time for each individual reforming operation must beworked out by a consideration of several factors. Thus the reformingtime factor is dependent upon the particular alkylate or otherisoparainic hydrocarbon stock being reformed, the catalyst, the ratio ofcatalyst to hydrocarbons, the efficiency of contact between catalyst andhydrocarbons, the temperature, the specication characteristics desiredin the reformed product, etc. Although the reaction may be speeded up byincreasing the temperature, increase in the temperature will in somecases produce an increase in the amount of side reactions such aspolymerization of any olens formed as intermediate products in thereforming reaction. Accordingly, even with non-oxidizing catalysts, thetemperature is generally kept below about 80 to 90 C. kIn general thereaction time used in carrying out the desired amount of rearrangementwill vary 'between about 1 and 24 hours. For a given set of conditionsof temperature, catalyst concentration, etc., one of the most importantfactors in determining the amount of time required for a particularreforming operation is the particular charge stock being subjected tothe process. The charge stocks of primary concern for reforming are thevarious octane and heptane alkylates, and the range of reaction timesgiven is generally suitable for these alkylates. With some of thehexanes, nonanes or decanes the range of reaction time is usuallygreater than the range given above, particularly where alkylationcatalysts less effective for the particular alkylate are used. The timerequired for reforming also varies with the particular alkylate isomersbeing treated. For example, the heptanes formed by the alkylation ofisopentane with ethylene are considerably slower in reforming 'to auniformly boiling hydrocarbon mixture, than the heptanes formed by thealkylation of isobutane with propylene. It is my belief, although myinvention should not be limited to any particular theoreticalconsiderations that under a given set of reaction conditions, thereaction time is primarily dependent upon the configuration of thecarbon atoms in the charge stock4 This discussion of reaction time isdirected to batch operation. Continuous processing, of course, permitsthe use of much shorter contact times as is well understood in the art.

It is difcult to state definitely which catalyst or catalysts willeffect the desired amount of reforming in the shortest period of time,since this also varies with charge stockA and the reaction conditions. Ihave found, however, that with certain alkylates one catalyst ispreferable, while with other alkylates another catalyst will bepreferred. For example, the heptanes formed Iby the alkylation ofisopentane with ethylene will be reformed most effectively with aluminumchloride, While the heptanes formed by the alkylation of isobutane withpropylene will be reformed by hydrogen fluoride substantially as rapidlyas with aluminum chloride. For the most part it may be stated that thosealkylation catalysts which are most effective for the formation of aparticular alkylate are most effective for its catalytic rearrangement.

Aluminum chloride and hydrofluoric acid have been mentioned above astypical catalysts suitable fcr my reforming process. It is to beunderstood that any hydrocarbon alkylation catalyst is likewisesuitable. The various catalysts must, of course, be used underconditions of temperature, pressure, concentration, etc., at which theyare effective as alkylation catalysts. rThe following are illustrativeof alkylation catalysts which are particularly useful in my process:hydrogen fluoride, sulfuric acid, aluminum chloride, aluminum bromide,and boron trifluoride. My invention is not, however, to be construed aslimited to the use of the aforementioned catalysts. In general, aluminumchloride represents the preferred catalyst for use with the less highlybranched-chain paranins, whereas hydrogen fluoride represents thepreferred catalyst for use with the more highly branched-chainparaflins. Aluminum .bromide corresponds rather closely to aluminumchloride, While sulfuric acid more nearly resembles hydrogen fluoride inits catalytic reforming properties.

I am aware that some of the alkylation catalysts will isomerize normalparaiinic hydrocarbons to produce branched-chain parafnic hydrocarbons.For example, Nenitzescu and Dragen have disclosed that aluminum chloridewill isomerize normal hexane and normal heptane to producebranched-chain hexanes and heptanes (of. Berichte, 66 B, 1892 (1933)).The isomerization of normal parafns to corresponding branched-chainhydrocarbons by aluminum bromide has been demonstrated by Glazebrook,Phillips and Lovell (cf. J. Am. Chem. Soc. 58, 1944 (1936)). Where theseisomerization processes are applied to the gasoline-boiling normalparaffins, there will be concurrent isomerization, cracking of thenormal parans to low boiling normal paran-ins, and reforming of theisomers produced. The isomerization of normal parailns is usuallyextremely slow under the comparatively mild conditions used forreforming the branched-chain paraflins. The boiling characterstics ofthe product from such a` combined processV isv not controllable-withinythe meaning withV which this term is used inmy invention.

The 'concurrent isomerization and reforming' of gasoline-boiling, normalparafns is not included within my invention. However, fractionation ofsuch a hydrocarbon mixture to separate out a narrow-boiling,branched-chain paraffin would yield a distillate fraction suitable fortreatment by my process to form a-hydrocarbon mixture of "desireddistillation characteristics within the gasoline range. `Therefore, thereforming of. a narrow-boiling,` branched-chain isoparaffin obtainedinthis way, as well as from any other source, is to be considered asincluded within the scope of my invention.

The catalysts used in my process are both hydrocarbon soluble andhydrocarbon insoluble catalysts. Aluminum bromide is a typicalvhydrocarbon soluble catalyst. The. hydrocarbon immiscible catalysts arefurther capable of division. into three groups based upon their physicalproperties under the reaction Aconditions as follows: solid, immisciblecatalysts, typied by-aluminum chloride; liquid, immiscible catalysts,typedby sulfuric acid and hydroiiuoric acid; yand gaseous catalysts,typied by gaseous hydrogen iiuOride.

Because of the different physicalcharacteristics ofv the variouscatalystsused, certaindifferences exist in the operating proceduresfollowed in the carrying out-of my invention.V The essentialfeaturesofrthelinvention arethe same, regardless of the particular type ofcatalyst selected.

, The gaseous catalysts may simply be bubbled up through the hydrocarboninoI packed tower, and this not only serves to produce contactbetweenhydrocarbon and catalyst, but WilLUina properly designed reactor,produce all'th'e fnecessary agitation. b flh catalyst, is veryeasilyrecirculateol for recontacting withhthe same batch ofhydrocarbons,V or with a fresh hydrocarbon fory treatment. HContinuousoperation is very easily performed. `n a yolumetric basis, the quantityof catalyst used is` fairly substantial relative tothe Aquantity ofhydrocarbon being reformed, thus requiring, in general,- more costly`equipment than with the other typev catalysts.

Solid, iinmiscible catalysts, such as aluminum fv"'c'zhlorida;possessthe advantage VthatV bulk separation ofthe liquidgasoline produced frm-'thesolid catalyst. is Very`simple. Considerableagitation is required with catalysts'Y of this type toobtain elcient"contacting Moreover, the all'irninum chloride reacts with someof'thehydrocarbons to forni" al sludge, Viizhose regeneration' involvesconsiderable additional processing.

Immiscible liquid catalysts suchas sulfuricacid and hydr'o'iluoric acidalso possess theadvant'age that bulk separation of product from thecatalyst involves a mere settling operation or its equivalent. furtheradvantage that, since itis quite stable and has a normal boilingpoint'of `19.4" C., it can be distilledV at ordinary temperatures andpres- Isuresyvithout decomposition. Therefore, the hydrogen fluoride`catalyst can be easily and cheaply puriiied as often as necessary by asimple distillation procedure whereby it may bevreused indelinitelyin myprocess. Hydrogen iluoride presents otheradvantages over sulfuric acidbecause of its lack of oxidizing effect-upon hydrocarbons per- I-drocarbon inimiscible layers-:4" f1 Y' In addition, hydrogen fluorideoifers the l Hydrocarbon soluble catalystssuch as aluminum bromide,possess the advantage that molecular contact is obtained betweencatalyst and hydrocarbon, hence a minimum of agitation is required. Thecatalyst may be'subsequently removed from thehydrocarbons by chilling,which will cause the catalyst to separate out as a solid, or bydistillation of the hydrocarbonsfrom the catalyst, preferably at reducedpressures.`

Because the reaction involved in my reforming process is of suiicientintensity to produce hydrocarbons boiling over the entire gasolinerange, therealso are produced smaller amounts of saturated hydrocarbonsboiling over andbelow the gasoline range. In this connection, I havefound that these less valuable saturated portions vof the reformedproduct distilling outside the gasoline range, e. g., below 25 C. andabove 168. C., can be utilized for the production of additionalgasoline-boiling hydrocarbons by reacting these products together in thepresence of essentially anhydrous hydrogen fluoride, or other alkylatingcatalyst. It should be noted that this reaction is not alkylation sinceboth reactants are saturated hydrocarbons.

Another feature of my invention is based upon my discovery that thedistillation characteristics of the nal product may be influencedby. theaddition of minor amounts of either light isoparains such as isobutaneor isopentane, or bythe addition of hydrocarbons boilingV above thegasoline range. The amount of this added hydrocarbon `should bepreferably less th-an an equimolar quantity, and is of the generalorder` of from V5 to about, 40 mol percent of .the alkylate chargestock. Since these light and heavy hydrocarbons are end products of thereforming reaction, their presence in the reaction mixture has theeffect, also, of slowing down the reforming reaction. Obviously, if toogreat a quantity of` these high and low boiling materials are present inthe mixture, the desired catalytic rearrangement will be largelysuppressed. As a general practice neither of these added hydrocarbonsshould be present in an amount much in excess of an equimolar quantityof the branched-chain hydrocarbon being reformed. As mentionedpreviously, the catalysts differ appreciably in their activity. Whilethe amount of either highor low-,boiling hydrocarbons added orrecirculated should be less than about an equimolar quantity (based uponthe hydrocarbons being reformed), and preferably should not exceed aboutfty mol percent, with some of the more active catalysts, or Where theextent of reforming desired is small, somewhat larger amounts of addedhydrocarbons may be present. In the case of aluminum chloride, forexample, amounts up to 200 mol percent of isobutane may be added, and insome cases'such a large addition might be desirable to enable bettercontrol of the extent of the reforming reaction. Without attempting totheorize as to the mechanics of the reaction by which a hexane, heptaneor an octane, for example, reacts to form isobutane, isopentane,hexanes, etc., up to 10to 12 carbon atom saturated hydrocarbons, I havefound that the presence of a low-boiling isoparaffin, such as isobutaneor isopentane, or a highboiling hydrocarbon, such as a decane, tends tosuppress the reaction towards the formation of these lower and higherboiling products. The result is the formation of a higher percentage ofintermediate boiling products, and a slowing downof there'a'ction.

agoaeae As stated previously, the highand low-boiling fractions may becombined andwill react together in the presence of an alkylationcatalyst under alkylating conditions of temperature and pressure to formadditional gasoline-boiling material. This may advantageously be done byrecycling these fractions to the reforming reactor. Normally, less than40 mol percent of the narrow-boiling feed is reformed to materialboiling outside of the gasoline range, even in the absence of addedhighor low-boiling material. Since the rate of recombination of thisrecirculated material is generally at least as rapid as the rate ofproduction of these highand low-boiling materials from thenarrow-boiling. feed, the total molar ratio of the high-.- andlow-boiling hydrocarbons to the narrow-boiling fraction in the reactionzone is less than 1 to l. In some cases Where the reforming reactionyields` substantial amounts of highand low-boiling material, of theorder of 30 to about 5I) mol percent, and/or the recombination of therecirculated highn and low-boiling feed material is slow, Vrelative toits rate of formation from the narrow-boiling feed, the amount of thehighand low-boiling material recirculated Will be larger than the amountof narrow-boiling fraction fed to the reaction zone. In such a case Ythetotal molar ratio of the recirculated hydrocarbons will exceed l to l..While this slows down the reforming of the narrowboiling fraction, sincegasoline-boiling material is being formedffroml the highand low-boilingmaterial, the overall result is the same; i. e., the formation Vof amaterial boiling over the entire, or a desired portion of the entire,gasoline range. In some casesit is possible that the amount oflow-boiling material formed maybe much in excess of the amount ofhigh-boiling material. If this is true, and if the amount of this excesslowboiling material (principally isobutane) is large relative to theamount of narrow-boiling hydrocarbonbeing processed, -it may benecessary to withdrawsome of this isobutane from` the process. In otherwords. where mol quantities of these recycled hydrocarbons are unequal,the mol excess of the one present in the greater amount should notexceed about 100 to 200 mol percent (depending upon the catalyst beingused) of the narrow-boiling hydrocarbon *being` processed. In the caseof this addition of highand low-boiling hydrocarbons, the high-boilingand low-boiling materials probably react with the branched-chainhydrocarbon being processed-as well as with each other. This samereaction between the reactant hydrocarbon being processed and recycledhydrocarbon or any added saturated i'soparaiiin undoubtedly occurs whereonly a single additionalV component is present. The exact mechanics .ofthe reaction occurring in a two or more component System is not clear,and my invention is not to be considered as bound to any theoreticalconsideration. The manner in which these added hydrocarbons affect thereaction is immaterial. The resulty is that `the catalytic'rearrangementfavors the formation'of less hydrocarbons boiling above and below thegasoline range. Where onlylone type of hydrocarbon is added,the.`material to be reformed should constitute at least 35 to 50 molvpercent of the total mixture. Asa consequence ofthe. eectfof these addedhydrocarbons, a simple procedure for controlling and regulating thedistillation characteristics of .the finall product is available.,

Y Inasmuch as my process involves theuse vof an alkylation catalyst forthe treatment of an alkylate charge stock, a simple andnovel combinedprocess is possible by using the same alkylation catalyst for thereforming step as was used` for the alkylation. In such a process, it isunnecessaryy to remove the alkylation catalyst from the alkylateproduct-containing, reaction mixture. Since it is usual to conductalkylation reactions with the use of a large excess of isoparafn, thisisoparafin should either be removed,V or, where its presence toinfluence the boiling range of the product is desirable, it may benecessary to only remove a part of it. In any event excess isoparaiinmust be removed to an extent which will allow the reforming reaction toproceed. The excess isoparailin should be reduced to less than 200 molpercent of the alkylate product, and preferably to less than mol percentof the alkylate. The product-catalyst mixture is reformed in the mannerheretofore described by further agitation and contacting beforeseparation. Therefore, another feature of my invention is a combinedalkylation and reforming operation. In such a combined process whereexcess isobutane, or other lightisoparaiiin is 'formed in the reformingstep as described previously, this light isoparanin may be used in thealkylation step tofmake additional narrowboiling alkylate. My inventionis not `to be construed, howeveizras limited to the use of the samecatalyst for the reforming as Was used for the' preparation of theinitial alkylate charge stock.

In FigureY l of the drawings there is shown diagrammatically a completeset up for both alkylating and reforming, wherein hydrogen fluorideis-the catalyst used in Iboth steps. In this operation a suitableisoparafn, such as isobutane, is fed through line I, provided withcontrol Valve `2, to a mixing chamber 3, wherein it is mixed with anolefin, such as propylene introduced through line Il, provided withcontrol valve 5. This mixture is then fed to reactor 6, in which astream. of concentrated hydrofluoric acid flows counter current to thehydrocarbon charge. This Aacid is recycled from the bottom of alkylator6, to the top thereof through line l,y by means of pump 8. The alkylate,principally heptanes along with unreacted isobutane and some entrainedacid passes from the top of the alkylator through. line 9, to settlingtank I0, Whereinthe hydrocarbons and acid separate to two layers. vTheacid leaves the bottom of this settlingtank through Aline II andisreturned to the alkylator along with the recycled acid passing throughline 1. The hydrocarbons flow from the settling tank through line I2, tofractionator I3, provided with suitable heating coil I4, wherein theisobutane isl removed from the alkylate as` overhead through line I5.Suitable means (not shown) are provided for returning some isobutane tothe'fractionatcr as reflux. The alkylateproduct from the bottom of thisfractionator flows through line IG, provided with pump Il, to reformerI8. In this reformer, as in the alkylator, a stream of concentratedhydrofluorlc acid flows counter current to the hydrocarbon charge.l lIhereformed hydrocarbons pass throughy line I9,to settling tank 20vvhereinthe mixture of hydrocarbons and entrained acidseparate into two layersin the manner previously described. The acid being recycled passes fromthe .bottom of the` reformer through line 2|, provided with pumps-x22,tothe top thereof. The acid layer from the settling tank 20, is`returned to the lbull:

oftheV recycled acid in line 2|, through line 23. The hydrocarbons fromthe settling tank 20, flow by line 24, to fractionator 25, provided witha suitable heating coil 26, wherein isobutane along with small amountsof isopentane are removed byi fractional distillation overhead throughline 21. Means (not shown) are provided for refluxing part of thefractionator overhead. The overhead from the fractionators in lines Iand 21, are combined in line 28, and returned to the isobutane feed lineI. lIfhis line 28 is provided with a suitable pump 29. The bottoms fromthe fractionator pass through lineal), provided with pump 3|, toscrubber 32, wherein the last traces of hydrogen fluoride are removed bywashing with an aqueous alkaline solution circulating through line 33,provided with pump v34. The scrubbed product ows through line 35, tostabilizer 36, where the gasoline fraction is removed by distillationthrough line 31, as an overhead product. The stabilizer is provided witha suitable heating coil 38, and means (not shown) are provided forreuxing part of the overhead. The bottoms from the stabilizer are fedback through line 39, either to the mixing chamber via line 49, or tothe reformer via line 4 I, wherein these bottoms are reacted in' thepresence of concentrated hydrouoric acid and the lighter isoparaiins togive additional quantities of gasoline-boiling range material. Valves 42and 43 are provided with lines 40 and 4l, respectively, whereby thedistribution of the return of the stabilized bottoms may be controlled.Line y44 is provided so that a suitable portion of the overhead fromfractionator 25 may be recycled directly to the reformer, although theselight isoparaffins may also 'be obtained in the reformer by regulatingthe amount of excess light isoparafn taken overhead from thefractionator I3. Valves 45 and 46 are provided for controlling thedistribution of the overhead from fractionator 25.

The following specic examples of operation are given to furtherillustrate the principles of my invention and the advantages obtained bymy process. These examples are illustrative only, and are not to be`construed as limiting the scope of my invention to the details setforth therein.

Example I A n alkylate charge stock composed principally ofbranched-chain heptanes in an amount of 4290 parts by Weight produced bythe reaction of isopentane with ethylene in the presence of anhydrousaluminum chloride, was mixed thor.. oughly with 1350 parts by'weight ofanhydrous aluminum chloride for 7 hours at room temperature in a steelautoclave. During this time a gradual pressure rise from about l toabout 8 pounds per square inch (gage) took place. This pressure rise wascaused by the formation of proportionately larger amounts of lightisoparafns having normally a higher vapor pressure than the alkylatecharge stock, and was used as a measure of the extent ofreaction.Agitation was then discontinued and the hydrocarbon phase separated fromthe catalyst, washed with water, and dried over .anhydrous calciumchloride. The dried hydrocarbons were then fractionated to recover thegasoline distilling in the range 25 to 160 C. f The properties of thisfraction and the original alkylate are given in the following table forcomparison: *Y f Gasoline Original fraction alkylate (25-160 C ofreformed product Octane rating, A. S. T. M. method: Y

No TEL 69. 9 74.8 83 '85 88.9 92.3

172 105 185 137 190 v182 192m 201 199 Y 222 L F .f'. 208 "310 Reid vaporpressure at F 4. 5 6.9

It will be noted that the gasoline-boiling.frac-U tion of the reformedproduct meets thedistilla.- tion Aand vapor pressure requirements foraviation gasoline and has an unleaded octane number almost 5 pointshigher than the original4 alkylate. It possesses the same high leadsusceptibility as the original alkylate, i. e., about 2.1.

The gaseous by-product distilling-below` 25 C. was composed entirely ofisobutane, and was reacted with the fraction distilling above 160 C. toproducean additional quantity of aviation boilingrange gasoline. Toillustrate the procedure for doing this the fraction distilling aboveC., which amounted to 439 parts by weight, was mixed thoroughly with 300parts by weight of isobutane and 240 parts by weight of anhydrousaluminumy chloride for 7 hoursatroomtemperature in a steel autoclave.During this time a gradual pressure drop from about29 to about 21 poundsper square inch (gage) took placer. `In this reaction there wasapressure drop sincethe the reaction products normally havea lesser vaporpressure than the original highand low-boiling fractions. As in theprevious ease, this change in the pressure was used as a measure oftheex-V tent of reaction. Agitationwas then. discontinued, the hydrocarbonphase separatedffrom the catalyst, and the gasoline fraction distillingin the range 25 to 160 C. recovered as inthe previous case. .Thisfractionamounted Vto., over 60 percent by weight of the total productand had approximately the same composition as the corresponding fractionobtained by catalytic` reforming of the original alkylate. l

By repeatedly reacting the light ends with the heavy ends and removingthe gasoline range material by fractionation, therefore; substantiallyall of the original alkylate can be converted to gasoline of high octanerating which meetsthe distillation and vapor pressure requirementsv foraviation gasoline. The continuous recycling procedure already describedis, of course, preferable for carrying out this process on a commercialscale. l

Example II 1380 parts by weight of alkylate' (principally branched-chainoctanes), having an octane nurnber by the A. S. T. M method of 93,produced by reaction of i'sobutane with normal butene in the presence ofconcentrated hydroiluoric acid, were mixed thoroughly with 1328 parts byweight of hydrofluoric acid for 15 hours at room temperature in a steelautoclave to obtain substantially complete reforming of this alkylate.During this time a gradual pressure rise from about 23- to about 27pounds per square inch (gage) took place, which was used as a measure ofthe extent of reaction. Affitation was then discontinued and the twoliquid phases, i. e., the hydrocarbon phase and the hydroiiuoric acidphase, allowed to separate. Thehydrouoric acid phase was withdrawn asthe bottom layer and the hydrocarbon phase washed with water, dried overanhydrous calcium chloride, and fractionated to recover the gasolinedistilling in the range 25 to 168 C.

The gaseous by-prcduct distilling below 25 C. was composed entirely ofisobutane, and was reacted with the fraction distilling above 168 C. toproduce an additional quantity of gasoline boiling range material. Toillustrate the procedure for doing this the fraction distilling above168 C. which amounted to 317 parts by weight was mixed thoroughly with216 parts by weight of isobutane and 447 parts by weight of concentratedhydrofluoric acid for 9 hours at room temperature in a steel autoclave.During this time a gradual pressure drop from about 40 to about 35pounds per square inch (gage) took place which, as in the previouscases, was used as a measure of the extent of reaction. Agitation wasthen discontinued, the two liquid phases separated, and the hydrocarbonphase fractionated as before to recover the gasoline fraction distillingin the range 25 to 168 C.

The properties of the composite gasoline prepared in this manner aregiven in the following table:

Plus 3 cc. No TEL TEL/gallon Octane rating:

A. S. T. M. method 84. 2 100. 0

Research 39 method. 83. 3 97.3

A. B. T. M. distillation: l

Vol. per cent distilled 10% 50% 70% 90% E. P.

Temperature, F 126 223 247 272 320 Reid vapor pressure at 100 F 8 poundsper square inch It Will be noted that this product has an A. S. T. M.octane number of 100 with only 3 cc. of tetraethyl lead per gallon.Substantially complete reforming was obtained in this case as shown bythe high vapor pressure and the appreciable quantity of lowandhigh-boiling hydrocarbons.

Example III Example IV The experiment described in Example III wasrepeated except that the time of contact between the hydrofluoric acidand the alkylate was 14 hours. The distillation curve, C, of the liquidproduct boiling above isopentane is given in Figure 2.

Ellample V The experiment described in Example III was repeated exceptthat a larger weight ratio of catalyst to alkylate was employed, i. e.,1.56 instead of 1.32, andthe time of contact between catalyst andalkylate was only 4 hours. The extent of reforming in this experimentfell midway between that obtained in the two previous examples as shownby the distillation curve, D, of the liquid product boiling aboveisopentane in Figure 2.

The following examples were performed to show the effect of an addedhydrocarbon, boiling outside the gasoline range on the reformingprocess.

Example VI The experiment described in Example IV was repeated exceptthat 46.5 mol percent of isobutane was added to the alkylate chargebefore contacting it with the acid for 14 hours. The extent of reformingin this experiment was appreciably less than that obtained in* theabsence of isobutane as shown by the distillation curve, E, of theliquid product in Figure 2.

Enample VII The experiment in Example III was repeated except that 104Ymol percent of isobutane was added to the alkylate charge beforecontacting it with the acid for 24 hours. Distillation curve F in Figure2 shows the extent of the reforming obtained in this experiment.

As mentioned above, the distillation curves for the products of ExamplesIII to VII boiling above isopentane Yhave been plotted in Figure 2. Thisgraph, wherein volume percent of gasoline-boiling material distilled isplotted againstV distillation temperature, effectively illustrates theutility of my invention. For comparison purposes, the distillation curveof the original heptane fraction obtained by the` alkylation ofisobutane with propylene is shown as curve A. This curve shows that thisheptane alkylate has a narrow-boiling range between and 100 C.

By a comparison of curve A with curves B, C, and D, the effect of thereforming reaction on the'boiling range of the alkylate fraction may bereadily seen. Approximately percent of the product boiling aboveisopentane distilled rather uniformly over the entire gasoline range.The lower-boiling material, not shown in the curves, constituted about30 percent of the original heptane fraction, and was about equallydivided between isobutaneand isopentane. The isopentane fraction is, ofcourse, suitable for use in gasoline, so about a total of 70 percent ofthe original heptane fraction was recovered directly as a gasolinefraction ofW uniform distillation characteristics over the entiregasoline boiling range.

Curves B, C, and D show the effect of time upon the reaction. The extentof reforming is substantially the same over the entire time range of 4to 24 hours. Curve B shows that somewhat more reforming was obtained at24 hours than at 14 hours shown in curve C. Where the reforming reactionwas allowed to proceed for only 4 hours, substantially the same degreeof reforming was obtained by slightly increasing the amount of catalystused, as shown by curve D lying intermediate curves B andk C.

A comparison of curves C and E shows the effect of an added hydrocarbonboiling outside the gaso-Y line range on the process. The effect of theadded hydrocarbon, isobutane, was to increase the proportion ofintermediate boiling material'. In the presence of isobutane (46.5 molprecent) over 65 percent of the material boiling above isopentane boiledwithin the range from 60 to 120 C. In the absence of isobutane onlyabout 45 percent of the material boiling above isopentane boiled in thissame range. The amount of material boiling above the gasoline range wasless than l percent, as compared with about 15 percent in the case ofreforming in the absence of isobutane. The amount of total low-boilingmaterial, not shown on the graph, was also considerably less, making thetotal gasoline-boiling material, including isopentane, about 85 percent.

Curve F shows that where the amount of isobutane added, in the case ofthe hydrofluoric acid catalyst, exceeded an equimolar quantity thereforming reaction was almost completely suppressed. The reaction wasallowed to proceed for 24 hours, and the curve shows that in thepresence of such a large amount of isobutane, an excessively long timewould be required to obtain appreciable reforming.

The curves show that in the absence of added isobutane, the contact timemay be varied from about one hour to about 24 hours without appreciablyaltering the results. 'I'his is evidence that with an active catalystequilibrium is established in the system in a comparatively short time.In case it is desired that the major fraction of the reformed productboil over but a limited portion of the gasoline range, contact times ofless than about one hour may be used, the concentration of the catalystmay be lowered, or a lowor highboiling hydrocarbon added.

It is important to note that the reformed product obtained by my processis not a low octane product as might be expected, but rather it hasY anoctane rating that compares favorably with that of the original alkylateand is frequently higher than that of the original alkylate. Whendealing with a narrow-boiling, branched-chain fraction of relatively lowoctane number, such as the ordinary heptane alkylates, the octane numberis raised in addition to obtaining a desired spread in the boilingrange. Some of the alkylates, such as the isobutane-butylene alkylate ofExample II, which have a very high octane number, will give a somewhatlower octane rating for the reformed product. The reformed product,however, might easily have a higher octane rating than the motor fuelobtained by blending the high octane alkylate with the blending agentsavailable and capable of giving the alkylate the proper boilingcharacteristics. Also a partial reforming of a high octane alkylate sothat it may I be blended with available blending agents to give acomplete motor fuel may frequently be desirable, and such a partialreforming could be accomplished at a lesser sacrice of octane number.The improvement in the boiling characteristics of the alkylate willfrequently be desirable and necessary for the effective utilization of aparticular alkylate, and for the production of a high octane completefuel. The process is therefore of value for the treatment of high octanealkylates as well as the lower octane alkylates, even though with theformer there is some sacrice in the octane number of the alkylateitself. The octane rating of my reformed products may be easily broughtup to aviation requirements by the addition of small and permissibleamounts of tetraethyl lead. It is also important to note that my processis capable of producing a complete gasoline, and that in so doing, alarger percentage of the alkylate, and hence a larger percentage ofgaseous hydrocarbons going into alkylate, will be represented in thefinished product.

The invention has been described with particular reference to alkylategasolines; however, it is to be understood narrow-boiling,branched-chain hydrocarbon fractions in general may be used. Forinstance, such a product formed by polymerizing olens and thenhydrogenating the polymers could serve as a stock to be reformed.

Many modifications of my invention will be apparent to those skilled inthe art, and only such limitations should be imposed as are indicated inthe appended claims.

I claim:

1. The process which comprises contacting a mixture of an isoparain andan olefin in which the mol ratio of the isoparaifln to the olen isgreater than two to one with an alkylation catalyst consistingessentially of hydrofluoric acid under alkylating conditions oftemperature and pressure for said catalyst to form a relativelynarrow-boiling alkylate, separating at least a sufficient amount of theisoparainn from the hydrocarbon product mixture to reduce theisoparafnalkylate mol ratio to less than one to one, contacting thealkylate product containing less than one mol of isoparaflin per mol ofalkylate with an alkylation catalyst consisting essentially ofhydrouoric acid under alkylating conditions of temperature and pressureto reform said alkylate to higher and lower boiling saturatedhydrocarbons, allowing the hydrocarbons and catalyst to remain incontact until the desired amount of the original narrow-boiling fractionhas been reformed to give a mixture of hydrocarbons whose boiling rangehas a desired distribution over the gasoline boiling range, separatingthe hydrocarbons from the hydrofluoric acid catalyst, fractionating thehydrocarbons to remove saturated hydrocarbons boiling below andsaturated hydrocarbons boiling above the desired range, returning thehydrocarbons so separated in admixture for further contacting with thealkylation catalyst, and recovering the desired hydrocarbon fraction ofcontrolled-boiling characteristics.

2. The process which comprises contacting a mixture of an isoparaflinand an olefin in which the mol ratio of isoparailin to the olefin isgreater than 2 to 1 with an alkylating catalyst consisting essentiallyof hydrofluoric acid under alkylating conditions of temperature andpressure for said catalyst to form a relatively narrow-boiling alkylate,separating a suiiicient amount of isoparai-lin from the hydrocarbonproduct mixture to reduce the isoparaffin-alkylate mol ratio to lessthan 1 to 2 contacting the alkylate product containing less thanone-half mol of isoparaflin per mol of alkylate product with analkylation catalyst consisting essentially of hydrofluoric acid underalkylating conditions of temperature and pressure to reform saidalkylate to higher and lower boiling saturated hydrocarbons, allowingthe hydrocarbons and catalyst to remain in contact until the desiredamount of the original narrow-boiling fraction has been reformed to givea mixture of hydrocarbons whose boiling range has a desired distributionover the gasoline boiling range, separating the hydrocarbons from thehydrouoric acid catalyst, fractionating the hydrocarbons to removesaturated hydrocarbons boiling below and saturated hydrocarbons boilingabove the desired range, returning the hydrocarbons so separated inadmixture for further contacting with the alkylation catalyst, andrecovering the desired hydrocarbon fraction of controlled boilingcharacteristics.

CARL S. KUHN, JR.

